Low-energy CO ₂ mineralization of asbestos-containing waste (ACW) via ammonium salt leaching: A route to detoxification and carbon sequestration

The safe management of asbestos-containing waste (ACW) remains an environmental and public health priority. This study proposes a low-energy treatment strategy integrating ammonium salt leaching with aqueous CO₂ carbonation to chemically stabilize fibrous asbestos structures. Although Ca²⁺ was not significantly leached from ACW using ammonium sulfate, the system achieved up to 99.9% conversion efficiency of dissolved Ca²⁺ to crystalline calcite (CaCO₃) during carbonation. XRD analysis confirmed the formation of calcite as the dominant product, and SEM images revealed the complete loss of fibrous morphology, replaced by rhombohedral carbonate layers. The ammonium-based process effectively modifies the surface of asbestos materials, forming a protective carbonate coating that limits fiber release. These results suggest that the addition of external Ca sources (e.g., CaO) may be required to ensure sufficient carbonation and full surface stabilization, given the low Ca leaching efficiency in ammonium salt systems. The process operates under ambient temperature and pressure, offering a safe and scalable alternative to thermal treatment methods for ACW stabilization.<i>Implications:</i> This study introduces a low-energy, scalable approach for the detoxification of asbestos-containing waste (ACW) through ammonium salt-assisted leaching and in situ CO₂ carbonation. By transforming hazardous fibrous asbestos into carbonate-coated, non-fibrous particulates, the method significantly reduces airborne toxicity while concurrently utilizing CO₂ as a reactive agent. The dual benefits of waste stabilization and carbon utilization position this process as a promising candidate for sustainable hazardous waste management and climate-responsive environmental engineering solutions.